1. Technical Field
The present invention relates to a pressure-regulating valve for properly vacuum-feeding a functional liquid to a functional droplet ejection head from a functional liquid feeding means; and to a liquid droplet ejection apparatus that is provided with the pressure-regulating valve.
2. Related Art
There is known a pressure-regulating valve for depressurizing a functional liquid of a sub tank to a predetermined pressure and feeding the functional liquid to a functional droplet ejection head, as described in Japanese Laid-open Patent Publication No. 2006-163733. This pressure-regulating valve is provided with a primary chamber communicating with an inflow port formed in a valve housing, and a secondary chamber communicating with an outflow port; a communication flow passage for communicating the primary chamber with the secondary chamber through a barrier; a valve body for opening and closing the communication flow passage from the primary chamber side, the edge of the opening of the communication flow passage on the primary chamber side being the valve seat; a diaphragm (pressure-receiving membrane) for forming one surface of the secondary chamber and opening and closing the valve body based on atmospheric pressure; and a valve body spring for urging the valve body in the closing direction. The valve housing, barrier, valve body, and other members constituting the pressure-regulating valve are formed of stainless steel or another corrosion-resistant metal in order to ensure solvent resistance and gas barrier properties with respect to the introduced functional liquid.
The valve body has an O-ring that comes in direct contact with the valve seat, and a valve holder that is formed by a holding part for holding the O-ring, and a shaft part that extends through the communication flow passage from the holding part. The communication flow passage is formed in a cruciform shape in cross-section, and the shaft part inserted through the communication flow passage is in contact with the diaphragm. Specifically, the valve body is opened and closed by the behavior of the diaphragm in a state in which the diaphragm and the valve body spring oppose each other.
However, in a pressure-regulating valve such as described above, although a small gap is formed between the communication flow passage and the shaft part of the valve body, since the communication flow passage is cruciform in cross-section, when the shaft of the valve body and the passage wall of the communication flow passage come in contact with each other as the valve body opens and closes, partial contact occurs and a relatively large sliding resistance is generated. Particularly because the wall of the communication flow passage and the shaft part of the valve body are both made of stainless steel or another metal, friction is high, the valve body is prevented from smoothly opening and closing, and the valve body no longer operates smoothly.